This invention relates to a hydraulic system. In particular, this invention relates to a hydraulic reservoir for connection to a hydraulic regenerative circuit.
Many mining machines or earth moving equipment utilize hydraulics to actuate movement of their components. During their operation, such machines may have pumps that draw hydraulic fluids into a cylinder to actuate a piston contained therein. Given the mass of the components driven by the expansion and/or retraction of the piston within the cylinder, great amounts of energy may be expended performing even the simplest movements, such as the raising and lowering of components.
Hydraulic regenerative circuits have been developed to recapture some of the energy on the return path of stroke. See e.g., U.S. Pat. Nos. 5,046,309; 6,438,951; and 7,562,615. Typically, as the hydraulic fluid is evacuated from the cylinder, the energy from the backwards flow of the fluid is captured in some way so that this energy can be used to power some other aspect the machine.
However, hydraulic regenerative circuits present unique problems for the storage and cleaning of the hydraulic fluid between stroke cycles. In many cases, the fluid changes in quality as it is used, and may become hot or dirty relative to the original fluid. On the return stroke, there is the potential for this hot, dirty fluid to mix with any cold, clean fluid in the reservoir. Accordingly, filtration and/or other processing of the used hydraulic fluid becomes difficult and it may be necessary to temporarily halt operation of the machine and/or replace the hydraulic fluid if the qualities of the hydraulic fluid become sufficiently unacceptable for use.
Hence, there is a need for improved hydraulic systems incorporating hydraulic regenerative circuits. In particular, there is a need for a hydraulic system that improves the utilization of the hydraulic fluid.